I think every format has it benefits and flaws. Tapes could be fantastic. I have almost no tapes that have deteriorated in use. There are some early 90's dubbed tapes with flutter/wow emerging, but it was just some cheap blank tapes where punk 7"s were being dubbed with pretty damn shitty gear. other than that, even tapes from early 80's, which sound brilliant today. It is surprising how often these days you do get shitty dubs or technically really weak quality tapes you need to first adjust manually to play properly.
I would not expect 40 years old CDR to even work. So many of them are unplayable already now. There are some brands that promised guarantees that their discs should last 100 years or so. Yet most discs used by labels and artists were of course cheapest stuff available out there. CDR format itself is chemically deteriorating. There is nothing one can do to prevent this, as it is part of format itself. After X amount of years laser will not be able to read it anymore. Until that happens, of course it's fairly reliable. Regular CD is different, so unless there was some pressing mistake (like the UK early 90's desaster), or mistreatment of disc, that'll last longer than anyone here. Anyone concerned of preserving sound, pressed cd is way to go. If wanting just something cheap and temporary - CDR is just fine.
Related:
I just had utmost horror with couple of Emil Beaulieau "Big foot" CDR's being totally destroyed. PVC sleeve, xerox covers.. this results the notorious chemical reaction many may be familiar with? What we had here, was that PVC reacted with cover and insert, and insert melted into both surfaces of CDR. When ripping paper off the pvc, and the disc, xerox ink and paper fragments had been melted into cdr - both sides. This is of course not CDR fault, but the PVC sleeve. I do recommend anyone having PVC sleeves on records or CDR with "diy covers" to check out condition for some surprises. Damn what a horror to see Aube "Pulse Resonator" LP+7" set PVC react with the cover... and the vinyl itself.